The non-covalent interaction of beta-ionone and beta-ionylidene acetaldehyde with opsin will be studied using circular dichroism spectroscopy. The binding constant will be determined and the temperature dependence of the binding constant will also be determined in order to ascertain the energies of interaction of each compound with the beta-ionone binding site of opsin. Visual pigment will be isolated from cattle and from invertebrate species and digested with proteolytic enzymes. Peptides containing the visual chromophore will be isolated and their spectral (UV and CD) and photochemical properties will be studied together with their regenerability.